Composite porous solid articles such as porous separation articles and carbon blocks are known in the art, wherein such articles are produced using mixtures of thermoplastic binders and interactive powdery or fibrous materials such as activated carbon powder. The articles generally are formed under conditions effective to permit the thermoplastic binder to connect the interactive powdery or fibrous materials in discrete spots, rather than as a complete coating. This arrangement permits the interactive powdery or fibrous materials to be in direct contact with, and to interact with, a fluid or gas. The resulting composite porous solid article is porous, thereby permitting the fluid or gas to penetrate into and even pass through the article. Such articles are useful in water purification, as well as in the separation of dissolved or suspended materials in both aqueous and non-aqueous systems in industrial uses. Examples of such composite porous solid articles, as well as methods for producing them, are described for example in WO 2014/055473 and WO 2014/182861, the entire disclosures of each of which are incorporated herein by reference for all purposes.
When producing such composite porous solid articles, it is important to ensure that the article is fully “cured” so that essentially all of the interactive powdery or fibrous material is bound securely into the article by the thermoplastic binder. The thermoplastic binder is heated to a temperature where the thermoplastic binder softens sufficiently that, upon cooling, the components of the mixture are fused together into a porous unitary body. Achieving full “curing” of the article will minimize the possibility that some portion of the interactive powdery or fibrous material remains capable of being dislodged from the composite porous solid article when the article is subjected to routine handling or normal use. For example, if the article is to be used for water purification, passing a volume of water through the article will not wash out any particles of the interactive powdery or fibrous material if the article has been fully cured. As another example, full curing will help improve the mechanical integrity of the article, thereby reducing the propensity of particles of the interactive powdery or fibrous material to separate from a surface of the article as the article is being manipulated (e.g., during the manual replacement of a carbon block in a filtration apparatus). While a greater degree of curing may generally be achieved by increasing the temperature at which a mixture of thermoplastic binder and interactive powdery or fibrous material is being formed into a composite porous solid article, excessive temperatures or heating conditions may cause an undesirable loss in the porosity of the article or in the ability of the powdery or fibrous material to interact with a fluid. Accordingly, establishing an optimum set of processing conditions for forming such a mixture into a composite porous solid article has proven to be challenging.